1. Field of the Invention
This invention relates to the manufacture of melt spun synthetic fibers having temperature regulation properties, the melt spun fibers being formed from polymer-based concentrate pellets that have Phase Change Materials (PCMs) therein.
2. Description of the Related Art
Many fabric materials are made from synthetic fibers. Two processesxe2x80x94a wet solution process and a melt spun processxe2x80x94are generally used for making synthetic fibers. The wet solution process is generally used to form acrylic fibers, while the melt spun process is used to form nylons, polyesters, polypropylenes, and other similar type fibers. A large portion of the fibers that are used in the textile industry are made via the melt spun process.
As is well known, nylon is a family of polyamide polymers characterized by the presence of the amide group CONH; polyester fiber is a fiber in which the fiber-forming substance is a long chain synthetic polymer composed of at least 85-percent by weight of an ester of a dihydric alcohol and terephthalic acid, and polypropylene (C3H5) is a synthetic crystalline thermoplastic polymer having a molecular weight of about 40,000 or more.
The melt spun manufacturing process generally involves passing a melted polymeric material or pellets through a device known as a spinneret, to thereby form individual polymeric fibers. The fibers are then made into a filament/strand, or into a cut staple. After the fibers have been formed, the fibers can be used to make non-woven material, or alternatively, the fibers can be wound into a yarn that is comprised of individual fibers, the yarn to be used thereafter in the weaving or knitting of a fabric material.
In order to provide a thermal regulation property to fabric materials, microencapsulated phase change materials (microPCMs or mPCMs) have been incorporated into acrylic fibers that were made using an aqueous batch (solution) process. However, with respect to synthetic fibers that are made by the melt spun manufacturing process wherein excessive amounts of volatile materials should not be present, conventional aqueous batch methods for incorporating mPCMs into the fibers are problematic.
It is against this background that embodiments of the present invention were developed.
According to one aspect of the present invention, disclosed herein is a process for manufacturing melt spinnable concentrate pellets that contain Phase Change Materials (PCMs), but do not contain an excessive amount of volatile materials. In accordance with this invention, the PCMs can be microencapsulated PCMs that are within the concentrate pellets, the PCMs can be absorbed into carrier polymers that form the concentrate pellets, and/or non-micro-encapsulated PCMs can be included as a component of the concentrate pellets.
According to the invention, the melt spinnable concentrate pellet matrix, or carrier polymer, can be any thermoplastic polymer or any combination of thermoplastic polymers
Concentrate pellets in accordance with the invention, can be blended into similar thermoplastic polymers, and the blend can then be extruded to form monofilament melt spun fibers, extruded films, injection molded products, etc., or the concentrate pellets can be blended with different thermoplastic polymers and the blend can then be extruded to form bicomponent or multi-component melt spun fibers, multi-component extruded films, multi-component injection molded products, etc.
For example, polypropylene concentrate pellets that contain PCMs or mPCMs can be blended with an additional amount of the polypropylene polymer and then melt spun to form polypropylene monofilament fibers, or this same polypropylene concentrate pellet can be blended with, or bicomponent melt spun with, an amount of nylon polymer to form bicomponent polypropylene/nylon fibers.
In accordance with a feature of the invention, but without limitation thereto, a PCM(s), and preferably a microencapsulate PCM(s), in a wet-cake form (i.e. in a water-based form) that comprises about 70 weight-percent solids and about 30 weight percent water, is melt-blended with a low molecular weight dispersing-polymer, with the result that about all of the water that is within the wet cake is driven off as the PCM(s) is concomitantly generally uniformly dispersed throughout the low molecular weight dispersing polymer.
In this mixture of a PCM(s) and a low molecular weight dispersing polymer, the dispersing polymer is selected for its compatibility with, and for its affinity for, the PCM(s), thus providing for an optimum dispersion of the PCM(s) throughout the dispersing polymer.
Granules of the above-described PCM/dispersion polymer are then melt blended with a high molecular weight polymer in order to produce concentrate pellets of the invention that contain about 15 weight percent of the PCM(s).
This high molecular weight polymer is selected for its affinity for the low molecular weight polymer and for the physical qualities that are desired of articles (i.e., fibers and the like) that are extruded, or melt spun in conventional manners using the concentrate pellets of the invention.
The foregoing and other features, utilities and advantages of the invention will be apparent from the following description of preferred embodiments of the invention.